Ribonucleases of the RNase III family are believed to be primarily responsible for the processing of double-stranded RNAs involved in post-transcriptional gene silencing in plants; see, for example, Jones-Rhoades et al. (2006) Annu. Rev. Plant Biol., 57:19-53 for a review of siRNA and mRNA biogenesis in plants. Since the requirements for plant and non-plant ribonucleases are not identical, double-stranded RNA can be designed to be resistant to plant ribonucleases but not to non-plant ribonucleases. In some cases, such as where a double-stranded RNA is to be transcribed in a plant cell but targets a non-plant gene, for example, a gene of a pest or a pathogen of the plant), it can be advantageous for the double-stranded RNA to remain relatively intact (e.g., not substantially processed by Dicer or Dicer-like proteins in planta) until it is taken up or contacted by the pest or pathogen.
This invention provides a recombinant DNA construct for plant cell transformation, including transcribable DNA including DNA that transcribes to an RNA for silencing a target gene of a pest or pathogen of a plant, wherein the RNA includes double-stranded RNA and has a stabilizing feature that imparts improved resistance to a plant RNase III enzyme relative to an RNA lacking the stabilizing feature. Constructs of the invention are particularly useful in making transgenic plant cells, plants, and seeds having in their genome a recombinant DNA construct of the invention, which imparts resistance to a pest or pathogen of the plant.
This invention further provides methods of providing a transgenic plant having improved resistance to a pest or pathogen of the plant. The transgenic plant can be directly grown from the transgenic plant cell (e.g., from transformed plant callus), or can be a transgenic progeny plant or seed, including an inbred or hybrid transgenic progeny plant or seed.
This invention further provides a composition for imparting to a plant resistance to a pest or pathogen of the plant, including an RNA for silencing a target gene of a pest or pathogen of a plant, wherein the RNA includes double-stranded RNA and has a stabilizing feature that imparts improved resistance to a plant RNase III enzyme relative to an RNA lacking the stabilizing feature. The composition of the invention optionally includes cells of the plant, an insect control agent; and/or a nematode control agent. Methods for using the composition are also provided.